Multilayered films are known. They are used for food packaging, for packaging medical supplies and sports articles and for speaker cones (see, for example, DE-OS 3 722 832).
Multilayered films are produced by coextrusion, extrusion coating and laminating.
For crash pad uses as outer skin for motor vehicle fittings it has hitherto been found satisfactory to use films based on PVC modified with various polymers. Such films are normally applied to a supporting structure and back foamed with polyurethane foam as they have no dimensional stability.
The requirements to be met by such films are:
they must easily be embossed, e.g. to produce a leather imitation, PA1 the embossed film must easily be shaped, PA1 the film must be resistant to conventional cleaning agents, PA1 the film must adhere to the material of the housing, PA1 a good impact strength, PA1 no release of gases (fogging), PA1 good strength of the grain at high temperatures. PA1 A a thermoplastic film 0.3 to 1.8 mm in thickness having a long term temperature resistance above 130.degree. C. and in particular having an E modulus of from 1000 to 20,000 MPa at temperatures from -40.degree. C. to +130.degree. C. and PA1 B a tough elastic film 0.4 to 1.5 mm in thickness composed of a mixture of
Films containing PVC can no longer fulfill the new requirements to be met by a crash pad film, namely long term temperature resistance of 130.degree. C. and dimensional stability without back foaming and without a supporting structure.
Numerous materials have been tested to see whether they meet these requirements but none has been satisfactory in all respects.
One main reason for this lies in the combination of properties required: use at high temperatures and stability of the leather grain at high temperatures.
Although materials (including multilayered films) have been developed which substantially fulfill the above mentioned combination of properties of so called crash pad films (leather substitute films in the motor vehicle sector), their use in practice has hitherto been found unsatisfactory on account of the lack of so called stability of the leather grain and the dimensional stability without the aid of a supporting structure.